1. Field of the Invention
The present invention relates to a cementitious composition for the molding of light-weight structural units and more particularly to a cementitious sand/stack dust/fly ash aggregate containing admixture which incorporates a significant proportion of a waste polyethylene material in strip form. The invention further embraces the method of preparing the cementitious composition for end use.
2. Description of the Prior Art
As is well-known in the building industry, molded blocks and other structural units are used quite extensively in the fabrication of masonry structures and the like. It is desirable that such blocks be relatively inexpensive, of a density suitable to allow fastening devices to be inserted therein, insulative, relatively light-weight, and yet sufficiently strong so as to be suitable for the desired utility. It is further desirable that such blocks present an appearance which is aesthetically pleasing. Recent attempts at satisfying each of these criteria with a single product have been adequate, but generally leave much to be desired.
For example, it is well-known in the prior art to utilize themoplastic additives in the form of pellets to provide compositions for the purpose of improving and varying their appearance. Of course, it seems apparent that the addition of such pellets will adversely affect, to a measurable degree, the load-bearing capabilities of the final product prepared from such a composition. Accordingly, the cement compositions are generally recommended for use only in relatively thin layers on top of another material such as a conventional concrete product.
Furthermore, in order to provide a pleasing appearance the thermoplastic additives must be of relatively uniform sizes and configurations. This necessarily increases the cost of such compositions and products prepared therefrom.
In an attempt to reduce the cost of cement compositions and end-use products manufactured from cement, the present state of the art recognizes the utilization of fly ash, which is an industrial waste, as an aggregate in the preparation of cement compositions. Of course, fly ash has also been used as a replacement for at least a portion of the portland cement element present in cement compositions.
More recently, as the availability of aggregate has diminished for commercial use there has been an attendant increase in the cost of cement mixtures and products made from cement. While the utilization of fly ash in cement composition is clearly a step in the right direction, both in conservation and in cost reduction, there is still a great need in the art for other cement-type products to meet the ever-increasing demand while at the same time maintaining a relatively stable cost factor. Accordingly, there is a need in the art for a novel composition for the molding of relatively light-weight structural units wherein heretofore useless waste materials may be utilized to produce a strong, insulative composition for the molding of structural units. Of course, such a cementitious composition should be able to withstand radical changes in temperature without seriously affecting the structural integrity of units manufactured therefrom, and it would further be desirable if the elements of such a composition could be selectively varied to render the composition suitable for the molding of structural units primarily desired for their insulative properties as opposed, for example, to structural units molded from a composition primarily intended to be utilized for their compressive strength. Finally, it is also desirable that such a composition provide an attractive appearance in the final end product.